The present invention relates to servo motor operated valves and particularly electrically operated valves of the type having a single inlet and plural outlets wherein a rotary valve member is progressively moved from an initial position blocking flow to one of the outlets and diverting flow to the remaining outlets progressively through positions permitting increasing flow through the one outlet and decreasing flow through the remaining outlets until full flow is directed through the one outlet.
Valves of this type are typically employed in a fluid flow circuit wherein it is desired in certain modes of operation to divert or bypass a portion of the flow for control purposes to a working fluid circuit and to divert the remainder of the flow away from the working load circuit such as to a sump or pump return.
The aforesaid type of bypass or diverted flow is desired in controlling flow of hot water or engine coolant to a heat exchanger or heater core for a motor vehicle passenger compartment climate control system, typically for heating the passenger compartment. In such automotive passenger compartment heaters, it is desired to control flow of the hot water to the heater core by diverting or bypassing a portion of the flow to the heater and directing the remaining portion to return to the engine coolant circuit or engine water pump inlet. Such an arrangement provides for accurate control of the flow of hot water to the heater core and thus gives the desired resolution of temperature control of the passenger compartment.
Heretofore bypass water valves for motor vehicle passenger compartment heater cores have typically been of the butterfly or rotary vane type which, have been employed because of their simplicity and low manufacturing cost, but which have the disadvantage or drawback of providing full flow between the closed position and about one-fourth of the full open position of the butterfly. This high gain change of flow with respect to rotary valve movement has caused the butterfly member in the valve to require a very fine control of its rotary position.
Where it has been desired to provide an electronically controlled automatic temperature control system for the vehicle passenger compartment, utilization of a motorized actuator for the bypass water valve has required extremely fine resolution of the motor actuator output and thus has proven to be difficult and costly with respect to the overall cost of the valve and heater system.
Thus, it has been desired to provide a bypass water valve for motor vehicle passenger compartment heater systems which provides accurate control of the flow and fine resolution of the flow with respect to movement of the valving member. It has further been desired to provide a linear relationship between the rotary movement of the valving member and the change in the diverted flow through the valve to the working load circuit.
Known servo motor actuated rotary water valves have required separate fasteners to attach the motor drive unit to the valve body, utilizing a sealing gasket and has the disadvantage of being a source of leakage and being costly in high volume mass production. It has thus been desired to provide such a servo motor actuated rotary valve for heater bypass flow control which provides linearity of control, simplicity of design and ease of assembly, robustness as to fluid seal integrity and reduced manufacturing cost.